Distinctive Features of Crack Growth Under Cyclic Loading at Elevated Temperature in the Context of Phase‐Field Fracture

The present work investigates the dominant failure mechanisms and crack growth behavior under isothermal and thermomechanical fatigue (TMF), analyzed in terms of energy release rate and phase‐field fracture modeling. The test material consisted of single‐edge notched tension (SENT) specimens fabricated from the nickel‐based heat‐resistant alloy XH73M. Experiments were conducted under conditions of pure fatigue, fatigue–creep interaction, and both in‐phase and out‐of‐phase TMF within the temperature range of 230°C to 650°C. Fractographic analysis based on fatigue fracture diagrams and scanning electron microscopy revealed characteristic features of crack propagation processes under thermomechanical loading. The experimental data on initial, current, and critical values of the energy release rate were incorporated into phase‐field fracture models to simulate the dominant intergranular and transgranular failure mechanisms in XH73M. Furthermore, the study establishes the limitations of employing conventional degradation functions for modeling cyclic fracture processes at elevated temperatures. Summary: The XH73M alloy tests performed for fatigue, creep–fatigue, in‐phase, and out‐of‐phase TMF. The dominant failure mechanisms for TMF are correlated with the energy release rate. The known equations for phase‐field fatigue degradation function have limited capabilities. The XH73M alloy dominant failure mechanisms are modeled by the Voronoi tessellation method.